EGFR and neoplasm: In the present work, two pseudoguaianolide SLs, neoambrosin (1) and damsin (2), were characterized from A. maritima L. Their anticancer activities against drug-resistant tumor cell lines were determined, in which either MDR-conferring ABC-transporters [P-glycoprotein (P-gp), BCRP, ABCB5] or mutation-activated EGFR were overexpressed.